Next let's talk about the attitude with which people approach the last part of the lives. NPR's Shankar Vedantam joins us regularly to talk about social science research and he's come across some research about what may influence our thinking about hanging on. Shankar, welcome back to the program.

SHANKAR VEDANTAM, BYLINE: Happy to be here, Steve.

INSKEEP: So what's the research?

VEDANTAM: Well, this is a study that looks at the effect of ageist stereotypes. These are negative stereotypes about the elderly on people's attitudes when it comes to medical decisions. The research was conducted in Portugal among elderly people by Sibila Marques and her collogues. And they wanted to find out whether these negative stereotypes could affect how people confront terminal illnesses.

INSKEEP: Meaning that people have this severe illness, they're facing decisions about how hard to fight and whether what - they think it's worth it?

VEDANTAM: That's exactly right. So what the researchers did was they exposed elderly people to positive and negative stereotypes about the elderly. So you can associate age with being insightful or mature or experienced, but you can also associate being elderly with negative stereotypes, such as being forgetful or dependent. And the researchers presented these descriptions to the volunteers subliminally, meaning the volunteers did not consciously realize they were being exposed to these ideas.

INSKEEP: Exposed them how then?

VEDANTAM: They flashed these words on a screen, but they flashed them for such a brief period of time...

INSKEEP: Oh, OK.

VEDANTAM: ...That people have no conscious recollection of having seeing these words. But there's been previous research which shows when you do this, the words essentially sink into your subconscious. The researchers then asked the volunteers to think about a medical situations where they faced a costly terminal illness, and they asked, do you want to pursue treatment or would you rather give up? And what they found is that the elderly volunteers exposed to the negative stereotypes had a significantly lower will to live than the volunteers that were exposed to the positive stereotypes.

INSKEEP: So if the word that flashed up was sage, you might want to live longer. If it said fogey or whatever, you would just say forget about it.

VEDANTAM: That's exactly the idea. And by the way, they ran the study with younger volunteers and they found, unsurprisingly, that younger volunteers were not affected by negative stereotypes about the elderly.

INSKEEP: So what is the lesson then for people who are in that situation or around a loved one who is in that situation?

VEDANTAM: Well, it's worth saying this was a small study, Steve, and the volunteers were not actually in a life or death situation. But I think what the study seems to suggest is that when you ask someone, do you want to fight a disease or do you want to let go. You're not just getting their conscious views on the subject, you might also be picking up their feelings about the stereotypes that are hanging in the air.